> You do need to be aware of the risks around whatever phone number you use to bootstrap your way in possibly being reallocated.

They recently added an optional "Registration Lock" feature to address this: https://support.signal.org/hc/en-us/articles/360007059792-Re...

This all has network effects. I have a smartphone, and I run Signal. But I run it much less, precisely because several people whom I want to interact with regularly are unable to, due to its limitation. This also means that I'm less likely to recommend it to others.

And I don't think that tablets are an "edge case". I mean, seriously? We're talking about millions of devices on the market. They may not be as popular as phones, but they are popular, and people use them. So when a guy uses, say, iMessage today, because it works across his iPhone and his iPad, I can't really pitch Signal to him. And that, again, has network effects.

It also seems to be the future. Phone numbers are how people receive phone calls, and more and more people are opting out of that in favor of instant messaging and video chat. More and more people have stopped answering their phones. Including our parents, who got sick of the scams and the robocalls. In my region, despite phone number portability, the numbers are fairly ephemeral with people switching to new ones all the time for all sorts of reasons. And nobody cares, because it is the IM system that is important.

Skype almost managed to replace the legacy phone network, but fell out of favor. If there was interoperability between clients like Signal, Whatsapp, Line, Wechat, it would take over a multi-billion dollar industry. Instead, my bank is trying to use some proprietary video conference system to schedule meetings with me.

This is another aspect of inter-portability that, I think, is often ignored. Matrix is doing great on this front. But then there's another concern here, which any Matrix/Riot user would have noticed - you interaction is as secure and private as the least secure of the two (or more for groups) clients in conversation - unless of course you enforce encryption which is also something you can do in a Matrix client. But it's nowhere near the WhatsApps and Telegrams when it comes to user of use.

Why don't you use it for SMS? At most 20% of my contacts use Signal, but for the rest of my non-Signal contacts I still use it to communicate using normal SMS/MMS without any hiccups, the only thing being the lack of encryption. I also personally prefer it to the IMO horrible default SMS apps provided by multiple vendors (including stock Android, at least up to V7).

People might be used to other SMS apps (better feature, familiarity etc) and Signal can't be used as an SMS app on iOS.

> Signal can't be used as an SMS app on iOS.

Sounds like a broken smartphone platform to me.

I'm not being glib: I really do believe that I should be easily able to replace any app on my phone. Android, while imperfect, is closer to that goal than is iOS, and so I use it, and recommend it to others.